Medium access control for wireless systems

ABSTRACT

A method for execution by a mobile station (MS) in a mobile communications network, the method comprising: receiving a first MS identifier from the network during a ranging operation involving the MS; using the first MS identifier to extract the contents of at least one message received from the network during said ranging operation; using a second MS identifier, different from the first MS identifier, to extract the contents of at least one message received from the network after said ranging operation is complete. Also, a method for execution by the base station, comprising: outputting a first message destined for the MS, the first message including a first identifier for use by the MS during a ranging operation; determining that said ranging operation is complete; outputting a second message destined for the MS, the second message including a second identifier for use by the MS in subsequent communication with the network.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional patentapplication No. 61/223,134 filed on Jul. 6, 2009, which is herebyincorporated by reference in its entirety.

This application is a continuation-in-part of the non-provisionalapplication (serial number tbd) resulting from conversion under 37C.F.R. § 1.53(c)(3) of U.S. provisional patent application No.61/223,134 filed on Jul. 6, 2009, which claims the benefit of U.S.provisional patent application No. 61/078,570 filed on Jul. 7, 2008.

MICROFICHE APPENDIX

Not applicable.

TECHNICAL FIELD

This application relates to wireless communication techniques.

BACKGROUND

Draft IEEE 802.16m System Description Document, IEEE 802.16m-08/003r1,dated Apr. 15, 2008, states that: “This [802.16m] standard amends theIEEE 802.16 WirelessMAN-OFDMA specification to provide an advanced airinterface for operation in licensed bands. It meets the cellular layerrequirements of IMT-Advanced next generation mobile networks. Thisamendment provides continuing support for legacy WirelessMAN-OFDMAequipment . . . The purpose of this standard is to provide performanceimprovements necessary to support future advanced services andapplications, such as those described by the ITU in Report ITU-RM.2072.”

Also, IEEE 802.16m System Requirements Document, IEEE 802.16m-07/002r4),states that: “Overhead, including overhead for control signaling as wellas overhead related to bearer data transfer, for all applications shallbe reduced as far as feasible without compromising overall performanceand ensuring proper support of systems features.”

SUMMARY

According to a first broad aspect, the present invention seeks toprovide a method for execution by a mobile station in a mobilecommunications network, the method comprising: receiving a first mobilestation identifier from the network during a ranging operation involvingthe mobile station; using the first mobile station identifier to extractthe contents of at least one message received from the network duringsaid ranging operation; using a second mobile station identifier,different from the first mobile station identifier, to extract thecontents of at least one message received from the network after saidranging operation is complete.

According to a second broad aspect, the present invention seeks toprovide a mobile station comprising: receive circuitry configured forreceiving messages from a network, at least one of the messages receivedduring a ranging operation and comprising a first mobile stationidentifier; a processing entity configured for extracting the contentsof at least one message received from the network during said rangingoperation based on the first mobile station identifier and forextracting the contents of at least one message received from thenetwork after said ranging operation is complete based on a secondmobile station identifier different from the first mobile stationidentifier.

According to a third broad aspect, the present invention seeks toprovide a computer-readable storage medium comprising computer-readableinstructions which, when executed by a computing entity in a mobilestation, cause the mobile station to: extract the contents of at leastone message received from a network during a ranging operation based onusing a first mobile station identifier; and extract the contents of atleast one message received from the network after said ranging operationis complete based on using a second mobile station identifier differentfrom the first mobile station identifier.

According to a fourth broad aspect, the present invention seeks toprovide A mobile station comprising: means for receiving messages from anetwork, at least one of the messages received during a rangingoperation and comprising a first mobile station identifier; means forextracting the contents of at least one message received from thenetwork during said ranging operation based on the first mobile stationidentifier; and means for extracting the contents of at least onemessage received from the network after said ranging operation iscomplete based on a second mobile station identifier different from thefirst mobile station identifier.

According to a fifth broad aspect, the present invention seeks toprovide A method for execution by a base station in a mobilecommunications network, comprising: outputting a first message destinedfor a mobile station, the first message including a first mobile stationidentifier for use by the mobile station during a ranging operation;determining that said ranging operation is complete; outputting a secondmessage destined for the mobile station, the second message including asecond mobile station identifier for use by the mobile station insubsequent communication with the network.

According to a sixth broad aspect, the present invention seeks toprovide A base station comprising: transmit circuitry configured foroutputting messages destined for a mobile station; a processing entityconfigured for determining when a ranging operation involving a mobilestation is complete, for inserting into a first one messages transmittedduring the ranging operation a first mobile station identifier for useby the mobile station during said ranging operation, and for insertinginto a second one of the messages a second mobile station identifier foruse by the mobile station after said ranging operation is complete.

According to a seventh broad aspect, the present invention seeks toprovide A computer-readable storage medium comprising computer-readableinstructions which, when executed by a computing entity in a basestation, cause the base station to: insert into a first message destinedfor a mobile station involved in a ranging operation a first mobilestation identifier for use by the mobile station during said rangingoperation; and insert into a second message destined for the mobilestation a second mobile station identifier for use by the mobile stationafter said ranging operation is complete.

According to an eighth broad aspect, the present invention seeks toprovide a base station comprising: means for outputting messagesdestined for a mobile station; means for determining when a rangingoperation involving a mobile station is complete; means for insertinginto a first one messages transmitted during the ranging operation afirst mobile station identifier for use by the mobile station duringsaid ranging operation; and means for inserting into a second one of themessages a second mobile station identifier for use by the mobilestation after said ranging operation is complete.

According to a ninth broad aspect, the present invention seeks toprovide A method for data transmission, comprising: accessing a memoryto obtain an amount of data associated with a service flow establishedwith a recipient and to be transmitted thereto; accessing the memory toobtain control information characterizing the service flow; formulatinga datagram by placing at least some of the data into a payload of thedatagram and placing, in a header of the datagram, the controlinformation characterizing the service flow, wherein the controlinformation characterizing the service flow occupies a fewer thansixteen bits of the header; modulating a radio frequency signal with thedatagram and releasing the radio frequency signal over a wirelessmedium.

Other aspects and features of the present application will becomeapparent to those ordinarily skilled in the art upon review of thefollowing description of specific embodiments of a disclosure inconjunction with the accompanying drawing figures and appendices.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present application will now be described, by way ofexample only, with reference to the accompanying drawing figures,wherein like reference numerals are used in different figures to denotesimilar elements.

FIG. 1 is a block diagram of a cellular communication system.

FIG. 2 is a block diagram of an example base station that might be usedto implement some embodiments of the present 5 application.

FIG. 3 is a block diagram of an example wireless terminal that might beused to implement some embodiments of the present application.

FIG. 4 is a block diagram of an example relay station that might be usedto implement some embodiments of the present application.

FIG. 5 is a block diagram of a logical breakdown of an example OFDMtransmitter architecture that might be used to implement someembodiments of the present application.

FIG. 6 is a block diagram of a logical breakdown of an example OFDMreceiver architecture that might be used to implement some embodimentsof the present application.

FIG. 7 is FIG. 1 of IEEE 802.16m-08/003r1, an Example of overall networkarchitecture.

FIG. 8 is FIG. 2 of IEEE 802.16m-08/003r1, a Relay Station in overallnetwork architecture.

FIG. 9 is FIG. 3 of IEEE 802.16m-08/003r1, a System Reference Model.

FIG. 10 is FIG. 4 of IEEE 802.16m-08/003r1, The IEEE 802.16m ProtocolStructure.

FIG. 11 is FIG. 5 of IEEE 802.16m-08/003r1, The IEEE 802.16m MS/BS DataPlane Processing Flow.

FIG. 12 is FIG. 6 of IEEE 802.16m-08/0030, The IEEE 802.16m MS/BSControl Plane Processing Flow.

FIG. 13 is FIG. 7 of IEEE 802.16m-08/003r1, Generic protocolarchitecture to support multicarrier system.

FIG. 14 is a flow diagram showing a message flow between a base stationand a mobile station involved in a ranging operation therewith, in thecase of initial network entry, in accordance with a specificnon-limiting embodiment of the present invention.

FIG. 15 conceptually illustrates a header of a medium access controlprotocol data unit (MAC PDU).

FIG. 16 shows a variant of the flow diagram in FIG. 14.

FIG. 17 shows another variant of the flow diagram in FIG. 14.

FIG. 18 is a flow diagram showing a message flow between a base stationand a mobile station involved in a ranging operation therewith, in thecase where the mobile station re-enters the network from an idle state,in accordance with a specific non-limiting embodiment of the presentinvention.

FIG. 19 is a flow diagram showing a message flow between a base stationand a mobile station involved in a ranging operation therewith, in thecase of a location update, in accordance with a specific non-limitingembodiment of the present invention.

FIG. 20 shows a state diagram of a mobile station, illustrating a numberof possible states, including an initialization state, an access state,a connected state and an idle state.

FIG. 21 shows in greater detail how the mobile station transitions intoand out of the initialization state.

FIG. 22 shows in greater detail how the mobile station transitions intoand out of the access state.

FIG. 23 shows in greater detail how the mobile station transitions intoand out of the connected state.

FIG. 24 shows in greater detail how the mobile station transitions intoand out of the idle state.

It is to be expressly understood that the description and drawings areonly for the purpose of illustration of certain embodiments of theinvention and are an aid for understanding. They are not intended to bea definition of the limits of the invention.

DETAILED DESCRIPTION

In the present disclosure, reference has been made to IEEE 802.16 andIEEE 802.16m. In the below, the term “IEEE 802.16” is meant to encompassversions of IEEE Std 802.16-, including but not limited to IEEE Std802.16-2004 and -2009, while the term “IEEE 802.16m” is meant toencompass versions of IEEE 802.16m-08, including but not limited to802.16m-08/003r3, and /003r1 and /003r9a. All of the foregoingdocuments, which are hereby incorporated by reference herein, areavailable from the IEEE, 3 Park Avenue, New York, N.Y. 10016-5997, USA,and can be consulted to in order to obtain additional backgroundinformation as to the context in which certain embodiments of thepresent invention may find application.

Referring to the drawings, FIG. 1 shows a base station controller (BSC)10 which controls wireless communications within multiple cells 12,which cells are served by corresponding base stations (BSs) 14. In someconfigurations, each cell is further divided into multiple sectors 13 orzones (not shown). In general, each BS 14 facilitates communicationswith mobile stations (MSs) 16, which are within the cell 12 associatedwith the corresponding BS 14. The MSs 16 can alternatively be referredto as mobile terminals, wireless stations, wireless terminals,subscriber stations, subscriber terminals, etc.

The movement of the MSs 16 in relation to the BSs 14 results insignificant fluctuation in channel conditions. As illustrated, the BSs14 and MSs 16 may include multiple antennas to provide spatial diversityfor communications. In some configurations, relayes (or relaystations—RSs) 15 may assist in communications between BSs 14 and MSs 16.MSs 16 can be handed off 18 from any cell 12, sector 13, zone (notshown), BS 14 or RS 15 to an other cell 12, sector 13, zone (not shown),BS 14 or RS 15. In some configurations, BSs 14 communicate with each andwith another network (such as a core network or the internet, both notshown) over a backhaul network 11. In some configurations, a BSC 10 isnot needed.

With reference to FIG. 2, an example of a BS 14 is illustrated. The BS14 generally includes a control system 20, a baseband processor 22,transmit circuitry 24, receive circuitry 26, multiple antennas 28, and anetwork interface 30. The receive circuitry 26 receives radio frequencysignals bearing information from one or more remote transmittersprovided by MSs 16 (illustrated in FIG. 3) and RSs 15 (illustrated inFIG. 4). A low noise amplifier and a filter (not shown) may cooperate toamplify and remove broadband interference from the signal forprocessing. Downconversion and digitization circuitry (not shown) willthen downconvert the filtered, received signal to an intermediate orbaseband frequency signal, which is then digitized into one or moredigital streams.

The baseband processor 22 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. As such, the baseband processor 22 is generallyimplemented in one or more digital signal processors (DSPs) orapplication-specific integrated circuits (ASICs). The receivedinformation is then sent across a wireless network via the networkinterface 30 or transmitted to another MS 16 serviced by the BS 14,either directly or with the assistance of a RS 15.

On the transmit side, the baseband processor 22 receives digitized data,which may represent voice, data, or control information, from thenetwork interface 30 under the control of control system 20, and encodesthe data for transmission. The encoded data is output to the transmitcircuitry 24, where it is modulated by one or more carrier signalshaving a desired transmit frequency or frequencies. A power amplifier(not shown) will amplify the modulated carrier signals to a levelappropriate for transmission, and deliver the modulated carrier signalsto the antennas 28 through a matching network (not shown). Modulationand processing details are described in greater detail below.

With reference to FIG. 3, an example of a MS 16 is illustrated.Similarly to the BS 14, the MS 16 will include a control system 32, abaseband processor 34, transmit circuitry 36, receive circuitry 38,multiple antennas 40, and user interface circuitry 42. The receivecircuitry 38 receives radio frequency signals bearing information fromone or more BSs 14 and RSs 15. A low noise amplifier and a filter (notshown) may cooperate to amplify and remove broadband interference fromthe signal for processing. Downconversion and digitization circuitry(not shown) will then downconvert the filtered, received signal to anintermediate or baseband frequency signal, which is then digitized intoone or more digital streams.

The baseband processor 34 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. The baseband processor 34 is generallyimplemented in one or more digital signal processors (DSPs) andapplication specific integrated circuits (ASICs).

For transmission, the baseband processor 34 receives digitized data,which may represent voice, video, data, or control information, from thecontrol system 32, which it encodes for transmission. The encoded datais output to the transmit circuitry 36, where it is used by a modulatorto modulate one or more carrier signals that is at a desired transmitfrequency or frequencies. A power amplifier (not shown) will amplify themodulated carrier signals to a level appropriate for transmission, anddeliver the modulated carrier signal to the antennas 40 through amatching network (not shown). Various modulation and processingtechniques available to those skilled in the art are used for signaltransmission between the mobile terminal and the base station, eitherdirectly or via the relay station.

In orthogonal frequency division multiplexing (OFDM) modulation, thetransmission band is divided into multiple, orthogonal carrier waves.Each carrier wave is modulated according to the digital data to betransmitted. Because OFDM divides the transmission band into multiplecarriers, the bandwidth per carrier decreases and the modulation timeper carrier increases. Since the multiple carriers are transmitted inparallel, the transmission rate for the digital data, or symbols, on anygiven carrier is lower than when a single carrier is used.

OFDM modulation utilizes the performance of an Inverse Fast FourierTransform (IFFT) on the information to be transmitted. For demodulation,the performance of a Fast Fourier Transform (FFT) on the received signalrecovers the transmitted information. In practice, the IFFT and FFT areprovided by digital signal processing carrying out an Inverse DiscreteFourier Transform (IDFT) and Discrete Fourier Transform (DFT),respectively. Accordingly, the characterizing feature of OFDM modulationis that orthogonal carrier waves are generated for multiple bands withina transmission channel. The modulated signals are digital signals havinga relatively low transmission rate and capable of staying within theirrespective bands. The individual carrier waves are not modulateddirectly by the digital signals. Instead, all carrier waves aremodulated at once by IFFT processing.

Orthogonal Frequency Division Multiple Access (OFDMA) is a multi-userversion of the OFDM digital modulation scheme. Multiple access isachieved in OFDMA by assigning subsets of subcarriers to individualusers. This allows simultaneous low data rate transmission from severalusers. Like OFDM, OFDMA employs multiple closely spaced sub-carriers,but the sub-carriers are divided into groups of sub-carriers. Each groupis named a sub-channel. The sub-carriers that form a sub-channel neednot be adjacent. In the downlink, a sub-channel may be intended fordifferent receivers. In the uplink, a transmitter may be assigned one ormore sub-channels. Sub-channelization defines sub-channels that can beallocated to MSs depending on their channel conditions and datarequirements. Using sub-channelization, within the same time slot a BScan allocate more transmit power to user devices (MSs) with lower SNR(Signal-to-Noise Ratio), and less power to user devices with higher SNR.Sub-channelization also enables the BS to allocate higher power tosub-channels assigned to indoor MSs resulting in better in-buildingcoverage. Sub-channelization in the uplink can save a user devicetransmit power because it can concentrate power only on certainsub-channel(s) allocated to it. This power-saving feature isparticularly useful for battery-powered user devices.

In operation, OFDM can be used for at least downlink (DL) transmissionfrom the BSs 14 to the MSs 16. Each BS 14 is equipped with “n” transmitantennas 28 (n>=1), and each MS 16 is equipped with “m” receive antennas40 (m>=1). Notably, the respective antennas can be used for receptionand transmission using appropriate duplexers or switches and are solabelled only for clarity. (When RSs 15 are used, OFDM may be used fordownlink transmission from the BSs 14 to the RSs 15 and from RSs 15 tothe MSs 16.)

In the uplink direction, the MS 16 may use the OFDMA digital modulationscheme. (When RSs 15 are used, OFDMA may be used for uplink transmissionfrom the BSs 14 to the RSs 15 and from RSs 15 to the MSs 16.)

It should be appreciated that the choice of OFDM in the downlink andOFDMA in the uplink is by no means limiting, and that other modulationschemes could be used.

With reference to FIG. 4, an example of a RS 15 is illustrated.Similarly to the BS 14, and the MS 16, the RS 15 will include a controlsystem 132, a baseband processor 134, transmit circuitry 136, receivecircuitry 138, multiple antennas 130, and relay circuitry 142. The relaycircuitry 142 enables the RS 15 to assist in communications between a BS14 and MSs 16. The receive circuitry 138 receives radio frequencysignals bearing information from one or more BSs 14 and MSs 16. A lownoise amplifier and a filter (not shown) may cooperate to amplify andremove broadband interference from the signal for processing.Downconversion and digitization circuitry (not shown) will thendownconvert the filtered, received signal to an intermediate or basebandfrequency signal, which is then digitized into one or more digitalstreams.

The baseband processor 134 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. The baseband processor 134 is generallyimplemented in one or more digital signal processors (DSPs) andapplication specific integrated circuits (ASICs).

For transmission, the baseband processor 134 receives digitized data,which may represent voice, video, data, or control information, from thecontrol system 132, which it encodes for transmission. The encoded datais output to the transmit circuitry 136, where it is used by a modulatorto modulate one or more carrier signals that is at a desired transmitfrequency or frequencies. A power amplifier (not shown) will amplify themodulated carrier signals to a level appropriate for transmission, anddeliver the modulated carrier signal to the antennas 130 through amatching network (not shown). Various modulation and processingtechniques available to those skilled in the art are used for signaltransmission between the mobile terminal and the base station, eitherdirectly or indirectly via a relay station, as described above.

With reference to FIG. 5, a logical OFDM transmission architecture willbe described. Initially, the BSC 10 will send data to be transmitted tovarious MSs 16 to the BS 14, either directly or with the assistance of aRS 15. The BS 14 may use the channel quality indicators (CQIs)associated with the mobile terminals to schedule the data fortransmission as well as select appropriate coding and modulation fortransmitting the scheduled data. The CQIs may be directly from the MSs16 or determined at the BS 14 based on information provided by the MSs16. In either case, the CQI for each MS 16 is a function of the degreeto which the channel amplitude (or response) varies across the OFDMfrequency band.

Scheduled data 44, which is a stream of bits, is scrambled in a mannerreducing the peak-to-average power ratio associated with the data usingdata scrambling logic 46. A cyclic redundancy check (CRC) for thescrambled data is determined and appended to the scrambled data usingCRC adding logic 48. Next, channel coding is performed using channelencoder logic 50 to effectively add redundancy to the data to facilitaterecovery and error correction at the MS 16. Again, the channel codingfor a particular MS 16 is based on the CQI. In some implementations, thechannel encoder logic 50 uses known turbo encoding techniques. Theencoded data is then processed by rate matching logic 52 to compensatefor the data expansion associated with encoding.

Bit interleaver logic 54 systematically reorders the bits in the encodeddata to minimize the loss of consecutive data bits. The resultant databits are systematically mapped into corresponding symbols depending onthe chosen baseband modulation by mapping logic 56. Quadrature AmplitudeModulation (QAM) or Quadrature Phase Shift Key (QPSK) modulation can beused, by way of example. The degree of modulation can be chosen based onthe CQI for the particular mobile terminal. The symbols may besystematically reordered to further bolster the immunity of thetransmitted signal to periodic data loss caused by frequency selectivefading using symbol interleaver logic 58.

At this point, groups of bits have been mapped into symbols representinglocations in an amplitude and phase constellation. When spatialdiversity is desired, blocks of symbols are then processed by space-timeblock code (STC) encoder logic 60, which modifies the symbols in afashion making the transmitted signals more resistant to interferenceand more readily decoded at a MS 16. The STC encoder logic 60 willprocess the incoming symbols and provide “n” outputs corresponding tothe number of transmit antennas 28 for the BS 14. The control system 20and/or baseband processor 22 as described above with respect to FIG. 5will provide a mapping control signal to control STC encoding. At thispoint, assume the symbols for the “n” outputs are representative of thedata to be transmitted and capable of being recovered by the MS 16.

For the present example, assume the BS 14 has two antennas 28 (n=2) andthe STC encoder logic 60 provides two output streams of symbols.Accordingly, each of the symbol streams output by the STC encoder logic60 is sent to a corresponding IFFT processor 62, illustrated separatelyfor ease of understanding. Those skilled in the art will recognize thatone or more processors may be used to provide such digital signalprocessing, alone or in combination with other processing describedherein. In an example, the IFFT processors 62 operate on the respectivesymbols to provide an inverse Fourier Transform. The output of the IFFTprocessors 62 provides symbols in the time domain. The time domainsymbols are grouped into frames, which are associated with a prefix byprefix insertion logic 64. Each of the resultant signals is up-convertedin the digital domain to an intermediate frequency and converted to ananalog signal via the corresponding digital up-conversion (DUG) anddigital-to-analog (D/A) conversion circuitry 66. The resultant (analog)signals are then simultaneously modulated at the desired RF frequency,amplified, and transmitted via the RF circuitry 68 and antennas 28.Notably, pilot signals known by the intended MS 16 are scattered amongthe sub-carriers. The MS 16, which is discussed in detail below, can usethe pilot signals for channel estimation.

Reference is now made to FIG. 6 to illustrate reception of thetransmitted signals by a MS 16, either directly from BS 14 or with theassistance of RS 15. Upon arrival of the transmitted signals at each ofthe antennas 40 of the MS 16, the respective signals are demodulated andamplified by corresponding RF circuitry 70. For the sake of concisenessand clarity, only one of the two receive paths is described andillustrated in detail. Analog-to-digital (A/D) converter anddown-conversion circuitry 72 digitizes and downconverts the analogsignal for digital processing. The resultant digitized signal may beused by automatic gain control circuitry (AGC) 74 to control the gain ofthe amplifiers in the RF circuitry 70 based on the received signallevel.

Initially, the digitized signal is provided to synchronization logic 76,which includes coarse synchronization logic 78, which buffers severalOFDM symbols and calculates an auto-correlation between the twosuccessive OFDM symbols. A resultant time index corresponding to themaximum of the correlation result determines a fine synchronizationsearch window, which is used by fine synchronization logic 80 todetermine a precise framing starting position based on the headers. Theoutput of the fine synchronization logic 80 facilitates frameacquisition by frame alignment logic 84. Proper framing alignment isimportant so that subsequent FFT processing provides an accurateconversion from the time domain to the frequency domain. The finesynchronization algorithm is based on the correlation between thereceived pilot signals carried by the headers and a local copy of theknown pilot data. Once frame alignment acquisition occurs, the prefix ofthe OFDM symbol is removed with prefix removal logic 86 and resultantsamples are sent to frequency offset correction logic 88, whichcompensates for the system frequency offset caused by the unmatchedlocal oscillators in the transmitter and the receiver. Thesynchronization logic 76 can include frequency offset and clockestimation logic 82, which is based on the headers to help estimate sucheffects on the transmitted signal and provide those estimations to thecorrection logic 88 to properly process OFDM symbols.

At this point, the OFDM symbols in the time domain are ready forconversion to the frequency domain using FFT processing logic 90. Theresults are frequency domain symbols, which are sent to processing logic92. The processing logic 92 extracts the scattered pilot signal usingscattered pilot extraction logic 94, determines a channel estimate basedon the extracted pilot signal using channel estimation logic 96, andprovides channel responses for all sub-carriers using channelreconstruction logic 98. In order to determine a channel response foreach of the sub-carriers, the pilot signal is essentially multiple pilotsymbols that are scattered among the data symbols throughout the OFDMsub-carriers in a known pattern in both time and frequency. Continuingwith FIG. 6, the processing logic compares the received pilot symbolswith the pilot symbols that are expected in certain sub-carriers atcertain times to determine a channel response for the sub-carriers inwhich pilot symbols were transmitted. The results are interpolated toestimate a channel response for most, if not all, of the remainingsub-carriers for which pilot symbols were not provided. The actual andinterpolated channel responses are used to estimate an overall channelresponse, which includes the channel responses for most, if not all, ofthe sub-carriers in the OFDM channel.

The frequency domain symbols and channel reconstruction information,which are derived from the channel responses for each receive path areprovided to an STC decoder 100, which provides STC decoding on bothreceived paths to recover the transmitted symbols. The channelreconstruction information provides equalization information to the STCdecoder 100 sufficient to remove the effects of the transmission channelwhen processing the respective frequency domain symbols.

The recovered symbols are placed back in order using symbolde-interleaver logic 102, which corresponds to the symbol interleaverlogic 58 of the transmitter. The de-interleaved symbols are thendemodulated or de-mapped to a corresponding bitstream using de-mappinglogic 104. The bits are then de-interleaved using bit de-interleaverlogic 106, which corresponds to the bit interleaver logic 54 of thetransmitter architecture. The de-interleaved bits are then processed byrate de-matching logic 108 and presented to channel decoder logic 110 torecover the initially scrambled data and the CRC checksum. Accordingly,CRC logic 112 removes the CRC checksum, checks the scrambled data intraditional fashion, and provides it to the de-scrambling logic 114 fordescrambling using the known base station de-scrambling code to recoverthe originally transmitted data 116.

In parallel to recovering the data 116, a CQI, or at least informationsufficient to create a CQI at the BS 14, is determined and transmittedto the BS 14. As noted above, the CQI may be a function of thecarrier-to-interference ratio (CR), as well as the degree to which thechannel response varies across the various sub-carriers in the OFDMfrequency band. For this embodiment, the channel gain for eachsub-carrier in the OFDM frequency band being used to transmitinformation is compared relative to one another to determine the degreeto which the channel gain varies across the OFDM frequency band.Although numerous techniques are available to measure the degree ofvariation, one technique is to calculate the standard deviation of thechannel gain for each sub-carrier throughout the OFDM frequency bandbeing used to transmit data.

In some embodiments, a relay station may operate in a time divisionmanner using only one radio, or alternatively include multiple radios.

Turning now to FIG. 7, there is shown an example network referencemodel, which is a logical representation of a network that supportswireless communications among the aforementioned BSs 14, MSs 16 and RSs15, in accordance with a non-limiting embodiment of the presentinvention. The network reference model identifies functional entitiesand reference points over which interoperability is achieved betweenthese functional entities. Specifically, the network reference model caninclude a MS 16, an Access Service Network (ASN), and a ConnectivityService Network (CSN).

The ASN can be defined as a complete set of network functions needed toprovide radio access to a subscriber (e.g., an IEEE 802.16e or an IEEE802.16m subscriber). The ASN can comprise network elements such as oneor more BSs 14, and one or more ASN gateways. An ASN may be shared bymore than one CSN. The ASN can provide the following functions:

-   -   Layer-1 and Layer-2 connectivity with the MS 16;    -   Transfer of AAA messages to subscriber's Home Network Service        Provider (H-NSP) for authentication, authorization and session        accounting for subscriber sessions    -   Network discovery and selection of the subscriber's preferred        NSP;    -   Relay functionality for establishing Layer-3 (L3) connectivity        with the MS 16 (e.g., IP address allocation);    -   Radio resource management.

In addition to the above functions, for a portable and mobileenvironment, an ASN can further support the following functions:

-   -   ASN anchored mobility;    -   CSN anchored mobility;    -   Paging;    -   ASN-CSN tunnelling.

For its part, the CSN can be defined as a set of network functions thatprovide IP connectivity services to the subscriber. A CSN may providethe following functions:

-   -   MS IP address and endpoint parameter allocation for user        sessions;    -   AAA proxy or server;    -   Policy and Admission Control based on user subscription        profiles;    -   ASN-CSN tunnelling support;    -   Subscriber billing and inter-operator settlement;    -   Inter-CSN tunnelling for roaming;    -   Inter-ASN mobility.

The CSN can provide services such as location based services,connectivity for peer-to-peer services, provisioning, authorizationand/or connectivity to IP multimedia services. The CSN may furthercomprise network elements such as routers, AAA proxy/servers, userdatabases, and interworking gateway MSs. In the context of IEEE 802.16m,the CSN may be deployed as part of a IEEE 802.16m NSP or as part of anincumbent IEEE 802.16e NSP.

In addition, RSs 15 may be deployed to provide improved coverage and/orcapacity. With reference to FIG. 8, a BS 14 that is capable ofsupporting a legacy RS communicates with the legacy RS in the “legacyzone”. The BS 14 is not required to provide legacy protocol support inthe “16m zone”. The relay protocol design could be based on the designof IEEE 802-16j, although it may be different from IEEE 802-16jprotocols used in the “legacy zone”.

With reference now to FIG. 9, there is shown a system reference model,which applies to both the MS 16 and the BS 14 and includes variousfunctional blocks including a Medium Access Control (MAC) common partsublayer, a convergence sublayer, a security sublayer and a physical(PHY) layer.

The convergence sublayer performs mapping of external network datareceived through the CS SAP into MAC SDUs received by the MAC CPSthrough the MAC SAP, classification of external network SDUs andassociating them to MAC SFID and CID, Payload headersuppression/compression (PHS).

The security sublayer performs authentication and secure key exchangeand Encryption.

The physical layer performs Physical layer protocol and functions.

The MAC common part sublayer is now described in greater detail.Firstly, it will be appreciated that Medium Access Control (MAC) isconnection-oriented. That is to say, for the purposes of mapping toservices on the MS 16 and associating varying levels of QoS, datacommunications are carried out in the context of “connections”. Inparticular, “service flows” may be provisioned when the MS 16 isinstalled in the system. Shortly after registration of the MS 16,connections are associated with these service flows (one connection perservice flow) to provide a reference against which to request bandwidth.Additionally, new connections may be established when a customer'sservice needs change. A connection defines both the mapping between peerconvergence processes that utilize the MAC and a service flow. Theservice flow defines the QoS parameters for the MAC protocol data units(PDUs) that are exchanged on the connection. Thus, service flows areintegral to the bandwidth allocation process. Specifically, the MS 16requests uplink bandwidth on a per connection basis (implicitlyidentifying the service flow). Bandwidth can be granted by the BS to aMS as an aggregate of grants in response to per connection requests fromthe MS.

With additional reference to FIG. 10, the MAC common part sublayer (CPS)is classified into radio resource control and management (RRCM)functions and medium access control (MAC) functions.

The RRCM functions include several functional blocks that are relatedwith radio resource functions such as:

-   -   Radio Resource Management    -   Mobility Management    -   Network Entry Management    -   Location Management    -   Idle Mode Management    -   Security Management    -   System Configuration Management    -   MBS (Multicast and Broadcasting Service)    -   Service Flow and Connection Management    -   Relay functions    -   Self Organization    -   Multi-Carrier        Radio Resource Management    -   The Radio Resource Management block adjusts radio network        parameters based on traffic load, and also includes function of        load control (load balancing), admission control and        interference control.        Mobility Management    -   The Mobility Management block supports functions related to        Intra-RAT/Inter-RAT handover. The Mobility Management block        handles the Intra-RAT/Inter-RAT Network topology acquisition        which includes the advertisement and measurement, manages        candidate neighbor target BSs/RSs and also decides whether the        MS performs Intra-RAT/Inter-RAT handover operation.        Network Entry Management    -   The Network Entry Management block is in charge of        initialization and access procedures. The Network Entry        Management block may generate management messages which are        needed during access procedures, i.e., ranging, basic capability        negotiation, registration, and so on.        Location Management    -   The Location Management block is in charge of supporting        location based service (LBS). The Location Management block may        generate messages including the LBS information.        Idle Mode Management    -   The Idle Mode Management block manages location update operation        during idle mode. The Idle Mode Management block controls idle        mode operation, and generates the paging advertisement message        based on paging message from paging controller in the core        network side.        Security Management    -   The Security Management block is in charge of        authentication/authorization and key management for secure        communication.        System Configuration Management    -   The System Configuration Management block manages system        configuration parameters, and system parameters and system        configuration information for transmission to the MS.        MBS (Multicast and Broadcasting Service)    -   The MBS (Multicast Broadcast Service) block controls management        messages and data associated with broadcasting and/or        multicasting service.        Service Flow and Connection Management    -   The Service Flow and Connection Management block allocates        “mobile station identifiers” (or station identifiers—STIDs) and        “flow identifiers” (FIDs) during access/handover/service flow        creation procedures. The mobile station identifiers and FIDs        will be discussed further below.        Relay Functions    -   The Relay Functions block includes functions to support        multi-hop relay mechanisms. The functions include procedures to        maintain relay paths between BS and an access RS.        Self Organization    -   The Self Organization block performs functions to support self        configuration and self optimization mechanisms. The functions        include procedures to request RSs/MSs to report measurements for        self configuration and self optimization and receive the        measurements from the RSs/MSs.        Multi-Carrier    -   The Multi-carrier (MC) block enables a common MAC entity to        control a PHY spanning over multiple frequency channels. The        channels may be of different bandwidths (e.g. 5, 10 and 20 MHz),        be on contiguous or non-contiguous frequency bands. The channels        may be of the same or different duplexing modes, e.g. Frequency        Division Duplexing (FDD), Time Division Duplexing (TDD), or a        mix of bidirectional and broadcast only carriers. For contiguous        frequency channels, the overlapped guard sub-carriers are        aligned in frequency domain in order to be used for data        transmission.

The medium access control (MAC) includes function blocks which arerelated to the physical layer and link controls such as:

-   -   PHY Control    -   Control Signaling    -   Sleep Mode Management    -   QoS    -   Scheduling and Resource Multiplexing    -   ARQ    -   Fragmentation/Packing    -   MAC PDU formation    -   Multi-Radio Coexistence    -   Data forwarding    -   Interference Management    -   Inter-BS coordination        PHY Control    -   The PHY Control block handles PHY signaling such as ranging,        measurement/feedback (CQI), and HARQ ACK/NACK. Based on CQI and        HARQ ACK/NACK, the PHY Control block estimates channel quality        as seen by the MS, and performs link adaptation via adjusting        modulation and coding scheme (MCS), and/or power level. In the        ranging procedure, PHY control block does uplink synchronization        with power adjustment, frequency offset and timing offset        estimation.        Control Signaling    -   The Control Signaling block generates resource allocation        messages. Sleep Mode Management block handles sleep mode        operation.        Sleep Mode Management    -   The Sleep Mode Management block may also generate MAC signaling        related to sleep operation, and may communicate with Scheduling        and Resource Multiplexing block in order to operate properly        according to sleep period.        QoS    -   The QoS block handles QoS management based on QoS parameters        input from the Service Flow and Connection Management block for        each connection.        Scheduling and Resource Multiplexing    -   The Scheduling and Resource Multiplexing block schedules and        multiplexes packets based on properties of connections. In order        to reflect properties of connections Scheduling and Resource        Multiplexing block receives QoS information from The QoS block        for each connection.        ARQ    -   The ARQ block handles MAC ARQ function. For ARQ-enabled        connections, ARQ block logically splits MAC SDU to ARQ blocks,        and numbers each logical ARQ block. ARQ block may also generate        ARQ management messages such as feedback message (ACK/NACK        information).        Fragmentation/Packing    -   The Fragmentation/Packing block performs fragmenting or packing        MSDUs based on scheduling results from Scheduling and Resource        Multiplexing block.        MAC PDU Formation    -   The MAC PDU formation block constructs MAC PDU so that BS/MS can        transmit user traffic or management messages into PHY channel.        MAC PDU formation block adds MAC header and may add sub-headers.        Multi-Radio Coexistence    -   The Multi-Radio Coexistence block performs functions to support        concurrent operations of IEEE 802.16m and non-IEEE 802.16m        radios collocated on the same mobile station.        Data Forwarding    -   The Data Forwarding block performs forwarding functions when RSs        are present on the path between BS and MS. The Data Forwarding        block may cooperate with other blocks such as Scheduling and        Resource Multiplexing block and MAC PDU formation block.        Interference Management    -   The Interference Management block performs functions to manage        the inter-cell/sector interference. The operations may include:        -   MAC layer operation        -   Interference measurement/assessment report sent via MAC            signaling        -   Interference mitigation by scheduling and flexible frequency            reuse        -   PHY layer operation        -   Transmit power control        -   Interference randomization        -   Interference cancellation        -   Interference measurement        -   Tx beamforming/precoding            Inter-BS Coordination    -   The Inter-BS coordination block performs functions to coordinate        the actions of multiple BSs by exchanging information, e.g.,        interference management. The functions include procedures to        exchange information for e.g., interference management between        the BSs by backbone signaling and by MS MAC messaging. The        information may include interference characteristics, e.g.        interference measurement results, etc.

Reference is now made to FIG. 11, which shows the user traffic data flowand processing at the BS 14 and the MS 16. The dashed arrows show theuser traffic data flow from the network layer to the physical layer andvice versa. On the transmit side, a network layer packet is processed bythe convergence sublayer, the ARQ function (if present), thefragmentation/packing function and the MAC PDU formation function, toform MAC PDU(s) to be sent to the physical layer. On the receive side, aphysical layer SDU is processed by MAC PDU formation function, thefragmentation/packing function, the ARQ function (if present) and theconvergence sublayer function, to form the network layer packets. Thesolid arrows show the control primitives among the CPS functions andbetween the CPS and PHY that are related to the processing of usertraffic data.

Reference is now made to FIG. 12, which shows the CPS control planesignaling flow and processing at the BS 14 and the MS 16. On thetransmit side, the dashed arrows show the flow of control planesignaling from the control plane functions to the data plane functionsand the processing of the control plane signaling by the data planefunctions to form the corresponding MAC signaling (e.g. MAC managementmessages, MAC header/sub-header) to be transmitted over the air. On thereceive side, the dashed arrows show the processing of the receivedover-the-air MAC signaling by the data plane functions and the receptionof the corresponding control plane signaling by the control planefunctions. The solid arrows show the control primitives among the CPSfunctions and between the CPS and PHY that are related to the processingof control plane signaling. The solid arrows between M_SAP/C_SAP and MACfunctional blocks show the control and management primitives to/fromNetwork Control and Management System (NCMS). The primitives to/fromM_SAP/C_SAP define the network involved functionalities such as inter-BSinterference management, inter/intra RAT mobility management, etc, andmanagement related functionalities such as location management, systemconfiguration etc.

Non-limiting examples of MAC management messages include DL-MAP, UL-MAP,DCD and UCD. Although nomenclature from IEEE 802.16 and/or 802.16m hasbeen adopted, it should be appreciated that strict compliance witheither standard is not a requirement, and that those skilled in the artwill recognize the use of common nomenclature as being an aid inunderstanding rather than a limitation of the present invention.

The DL-MAP and UL-MAP can be used to define access to the downlink anduplink information respectively. The DL-MAP is a MAC management messagethat defines burst start times on the downlink. Equivalently, the UL-MAPis a set of information that defines the entire (uplink) access for allMSs during a scheduling interval. Basically, the DL-MAP and UL-MAP canbe viewed as directories, broadcasted by the BS, of downlink and uplinkframes.

The DCD (Downlink Channel Descriptor) message is a broadcasted MACmanagement message transmitted by the BS 14 at a periodic time intervalin order to provide the burst profiles (physical parameter sets) thatcan be used by a downlink physical channel during a burst, in additionto other useful downlink parameters. The UCD (Uplink Channel Descriptor)message is a broadcasted MAC management message transmitted by the BS ata periodic time interval in order to provide the burst profile (physicalparameter sets) description that can be used by an uplink physicalchannel in addition to other useful uplink parameters.

Reference is now made to FIG. 13, which shows a generic protocolarchitecture to support a multicarrier system. A common MAC entity maycontrol a PHY spanning over multiple frequency channels. Some MACmessages sent on one carrier may also apply to other carriers. Thechannels may be of different bandwidths (e.g. 5, 10 and 20 MHz), be oncontiguous or non-contiguous frequency bands. The channels may be ofdifferent duplexing modes, e.g. FDD, TDD, or a mix of bidirectional andbroadcast only carriers.

The common MAC entity may support simultaneous presence of MSs 16 withdifferent capabilities, such as operation over one channel at a timeonly or aggregation across contiguous or non-contiguous channels.

FIG. 20 illustrates a possible state transition diagram for a MS 16. Byway of non-limiting example, the diagram shows four (4) states,Initialization state, Access state, Connected state and Idle state.

Initialization State

-   -   In the Initialization state (see FIG. 21), the MS 16 performs        cell selection by scanning, synchronizing and acquiring the        system configuration information before entering Access state.        If the MS 16 cannot properly perform the system configuration        information decoding and cell selection, it returns to perform        scanning and downlink synchronization. If the MS 16 successfully        decodes the information and selects a target BS 14, it        transitions to the Access state.        Access State    -   In the Access state (see FIG. 22), the MS 16 performs network        entry with the target BS 14. Network entry is a multi step        process consisting of ranging, pre-authentication capability        negotiation, authentication and authorization, capability        exchange and registration.    -   The breakdown of the system entry procedure leading from        downlink scanning and synchronization to the point where a        connection is established can be as follows, by way of        non-limiting example:        -   Downlink scanning and synchronization and acquisition of            granting message (which grants uplink resource) and            acquisition of description of downlink channel and uplink            channel;        -   Initial ranging        -   Capability negotiation        -   Authorization and authentication/key exchange        -   Registration with BS 14        -   Connection establishment    -   Upon failure to complete network entry, the MS 16 may transition        to the Initialization state.        Connected State    -   When in the Connected state the MS 16 may operate in one of 3        modes (see FIG. 23): Sleep mode, Active mode and Scanning mode.        During the Connected state, the MS 16 can maintain one or more        fundamental connections established during Access state.        Additionally the MS 16 and BS 14 may establish additional        transport connections. The MS 16 may remain in the Connected        state during a handover. The MS 16 may transition from the        Connected state to the Idle state on a command from the BS 14.        Failure to maintain the fundamental connection(s) may also        prompt the MS 16 to transition to the Initialization state.    -   Referring now to the modes of operation in the Connected state,        when the MS 16 is in Active mode, the BS 14 may schedule the MS        16 to transmit and receive at the earliest available opportunity        provided by the protocol being implemented, i.e. the MS is        assumed to be ‘available’ to the BS 14. The MS 16 may request a        transition to either Sleep or Scanning mode from Active mode.        Transition to Sleep or Scanning mode can happen on command from        the BS 14. The MS 16 may transition to Idle state from Active        mode of the Connected state.    -   When in Sleep mode, the MS 16 and BS 14 agree on a division of        the resources in time into Sleep Windows and Listening Windows.        The MS 16 is only expected to be capable of receiving        transmissions from the BS 14 during the Listening Windows and        any protocol exchange has to be initiated during that time. The        MS 16 transition to Active mode is prompted by control messages        received from the BS 14. The MS 16 may transition to Idle state        from Sleep mode of the Connected state during Listening        Intervals.    -   When in Scanning mode, the MS 16 performs measurements as        instructed by the BS 14. The MS 16 is unavailable to the BS 14        while in scanning mode. The MS 16 returns to Active mode once        the duration negotiated with the BS 14 for scanning expires.        Idle State    -   The Idle state (see FIG. 24) may, by way of non-limiting        example, include 2 separate modes, namely Paging Available mode        and Paging Unavailable mode, based on its operation and MAC        message generation. During the Idle state, the MS 16 may perform        power saving by switching between Paging Available mode and        Paging Unavailable mode.    -   Idle Mode, the MS 16 may belong to one or multiple paging        groups. When in Idle mode, the MS 16 may be assigned paging        groups of different sizes and shapes based on user mobility. The        MS 16 monitors the paging message at during the MS's Paging        Listening Interval. The start of the MS's Paging Listening        Interval is derived based on paging cycle and paging offset.        Paging offset and paging cycle can be defined in terms of number        of superframes.    -   The MS 16 may thus be paged by the BS 14 (using a specialized        paging message) while it is in the Paging Available mode. If the        MS 16 is paged with indication to return to the Connected state,        the MS 16 transitions to the Access state for its network        re-entry.    -   The MS 16 may also perform a location update procedure during        Idle State.    -   During Paging Unavailable mode, MS 16 does not need to monitor        the downlink channel in order to reduce its power consumption.

The MS has a global address (or global identifier) and logical addresses(or logical identifiers) that identify the MS 16 during operation.Specifically, the global address can be a globally unique 48-bit IEEEExtended Unique Identifier (EUI-48™) based on the 24-bitOrganizationally Unique Identifier (OUI) value administered by the IEEERegistration Authority. However, this is not a limitation or restrictionof the present invention.

As far as the logical identifiers are concerned, these can include oneor more “flow identifiers” (FIDs) and one or more “mobile stationidentifiers”. The FIDs can uniquely identify management connections andtransport connections that the MS 16 has established with the network.Some specific FIDs may be pre-assigned. For their part, the mobilestation identifiers uniquely identify the MS 16 within the domain of theBS 14. Various types of STID could be as follows:

-   -   Access ID: a temporary identifier assigned to the MS 16 when        performing a ranging operation (i.e., upon network entry while        in the Access state or upon network re-entry or during a        location update while in the Idle state). This ID can be        assigned to the MS 16 by the BS 14 when the BS 14 first detects        a ranging code transmission from the MS 16.    -   MS ID: an identifier assigned to the MS 16 for use in the        Connected state. The MS ID replaces the Access ID and can be        sent to the MS 16 during the ranging operation. Downlink control        information dedicated to a particular MS (e.g. downlink PHY        burst/resource allocation) can be addressed using the MS ID. The        MS ID may, but need not be, be the same length as the Access ID        identifier.    -   Idle ID: an identifier assigned to an MS for use in the Idle        state. In order to reduce signaling overhead and provide        location privacy, the Idle ID can be assigned to uniquely        identify those MSs in the Idle state that are in a particular        paging group. The Idle ID remains valid for the MS 16 as long as        the MS 16 stays in the same paging group. The Idle ID may be        assigned during Idle state entry or during location update due        to a paging group change. The Idle ID can be included in a        message sent by the MS 16 in the Idle state for the purposes of        page response or location update.

By way of example, the mobile station identifiers mentioned above couldbe 8 bits, 10 bits or 12 bits in length, although longer or shorterSTIDs are possible without departing from the present invention.Different mobile station identifiers can be of different lengths. Forexample, the Access ID could be the same length and the MS ID, both ofwhich could be shorter than the Idle ID. However, this is only anexample and is not to be considered limiting. Other mobile stationidentifiers may exist and could be reserved, for example, for broadcastor multicast services.

As will be appreciated by those of skill in the art, a MAC PDU is apackage of data (group of data bits, or datagram) that contain header,connection address and data protocol information that is used to controland transfer information across a type of medium (such as a radiochannel). With reference now to FIG. 15, the MAC PDU created inassociation with a given connection contains a header, which holds thecorresponding FID along with control information (e.g., a length field,which indicates the length of the payload of the MAC PDU and an ExtendedHeader (EH) bit which, if set, indicates that additional informationappears in an extended portion (not shown) of the header). The MAC PDUmay also have payload of data and error checking bits (CRC) bits afterthe header (e.g. user data). The payload may be used to carry managementmessages and data associated with various traffic connections.

Being local to the MS, each FID is shorter than the 16-bit CID definedin IEEE Standard 802.16-2004 or IEEE Standard 802.16-2009. In onenon-limiting embodiment, the HD can be of length 4 bits. In anothernon-limiting embodiment, the FID can be of length 3 bits. Otherpossibilities exist within the scope of the present invention. The useof the FID in the MAC header also results in a shorter overall MACheader than the ones proposed in IEEE 802.16-2004 or IEEE 802.16-2009,where the 16-bit CID is used.

The following now describes a ranging operation that can be performed bythe MS 16 and the BS 14 in order to establish connectivity. The rangingoperation is performed by the appropriate functional blocks describedabove and, in particular, the functional blocks belonging to the MediumAccess Control (MAC) Common Part Sublayer (CPS). These functional blocksmay include, for example and without limitation, the Network EntryManagement block and the Idle Mode Management block (part of the radioresource control and management—RRCM—functions), as well as the PHYControl block (part of the medium access control—MAC—functions)described earlier in connection with FIG. 10.

Three non-limiting scenarios of the ranging operation will be described,namely Scenario A in which the MS 16 is seeking to establish initialconnectivity to the network (i.e., the MS 16 is powered up, goes throughthe Initialization state and performs ranging from the Access state),Scenario B in which the MS 16 performs ranging upon re-entering thenetwork (e.g., after having been in the Idle state, after having leftthe network to use a different one, then returned (i.e., roaming),etc.), and Scenario C in which the MS 16, after having been in the Idlestate, performs ranging in the context of a location update.

Scenario A

In Scenario A, the MS 16 is seeking to establish initial connectivity tothe network. Firstly, the MS 16 is powered up and goes through theInitialization state. During the Initialization state, the MS 16performs scanning and synchronization. In other words, when the MS 16wants to join the network, it first scans the downlink frequencies tosearch for a suitable channel. The search is complete as soon as itdetects a downlink frame. The next step is to establish synchronizationwith the BS 14. Once the MS 16 receives a DL-MAP message and a DCDmessage, the downlink synchronization phase is complete and the MS 16remains synchronized as long as it keeps receiving DL-MAP and DCDmessages. After the synchronization is established, the MS 16 waits fora UCD message to acquire uplink channel parameters.

A ranging operation now takes place while the MS 16 is in the Accessstate. With reference to FIG. 14, the BS 14 issues an uplink grantingmessage 1410 (e.g., a UL-MAP message) which defines an initial ranginginterval to be used by the MS 16 in the uplink frame. The contents ofthe uplink granting message could be formulated by an uplink schedulerin the BS 14. The uplink scheduler manages uplink bandwidth, andschedules MSs that will be allocated uplink grants based on the QoSrequirements of their service flow(s) and bandwidth requests. An uplinkgrant allocated by the uplink scheduler is directed towards a reservedFID (e.g., broadcast) and can use a predefined robust profile with BPSK½ modulation/FEC, for example. After transmission of granting message1410, the BS 14 continues to operate normally (1412). This includes theperiodic issuance of other granting messages, such as granting message1422.

Meanwhile, as shown at 1412, the MS 16 has been waiting for receipt of agranting message and is assumed to ultimately receive granting message1410. Upon receipt of the granting message 1410, the MS 16 formulates aranging message 1416 characterized by a set of ranging resources. Forexample, the MS 16 can select, at random, a code from a set ofpseudonoise ranging codes, modulate it onto a ranging subchannel, andsubsequently transmit it in a randomly selected ranging slot from amonga set of available ranging slots on the uplink frame. The MS 16 can userandom selection or random backoff to select a ranging slot. When randomselection is used, the MS 16 can select one ranging slot from allavailable slots in a single frame using a uniform random process,although other possibilities exist. When random backoff is used, the MS16 can select one ranging slot from all available ranging slots in acorresponding backoff window using a uniform random process, forexample.

If the BS 14 properly detects the presence of the ranging code in theranging slot of ranging message 1416, then the BS 14 issues a rangingresponse message to the MS 16. For example, the ranging response messagecould take a form similar to an RNG-RSP message as defined in IEEE802.16 or 802.16m. In anticipation of this event, at step 1426, the MS16 determines whether an RNG-RSP message has been received from the BS14. If a certain amount of time has elapsed, and a RNG-RSP message hasnot been received, then this means that the BS 14 has not properlydetected the presence of the ranging code in the ranging slot of rangingmessage 1416. This could be for a variety of reasons, including powerissues, interference, etc. Meanwhile, the MS 16 is also attentive toreceipt of further granting messages (step 1420). If indeed theaforementioned granting message 1422 is received without havingreceiving an intervening RNG-RSP message from the BS 14, then the MS 16will be granted a new ranging interval in an uplink frame.

In response, and similar to what was described earlier, the MS 16formulates a ranging message 1424 that is characterized by a set ofranging resources. Specifically, the MS 16 selects, at random, a codefrom a set of pseudonoise ranging codes, modulates it onto a rangingsubchannel, and subsequently transmits it in a randomly selected rangingslot from among a set of available ranging slots on the uplink frame,and returns to step 1426. If the BS 14 properly detects the presence ofthe ranging code in the ranging slot of ranging message 1424, then theBS 14 will issue a ranging response message to the MS 16. Inanticipation of this event, at step 1426, the MS 16 determines whether aranging response message has been received from the BS 14. If a certainamount of time has elapsed, and a ranging response message still has notbeen received, then the MS 16 will receive yet another granting messageat step 1420 and so on. However, if the BS 14 does properly detect thepresence of the ranging code in the ranging slot of ranging message 1424(step 1428), then the BS 14 will determine whether the ranging operationis successful (step 1430). In other words, just because the BS 14 canhear the MS 16 does not mean that the MS 16 is using adequate power,timing and frequency parameters.

Thus, the outcome of step 1430 may be that the BS 14 has determined thatthe ranging operation was a success, in which case the BS 14 proceeds toissue a ranging response message 1450 indicative of this determination.On the other hand, the outcome of step 1430 may be that the BS 14 hasdetermined that the ranging operation was not a success. In this case,the BS 14 proceeds to step 1432 where a parameter adjustment iscalculated. This may affect one or more of the frequency, timing andpower that characterize the signaling used by the MS 16. Variousalgorithms can be used to determine an adjustment of the power, timingand/or frequency characteristics of the uplink signal. Also at step1432, the BS 14 calculates a new ranging code and/or a new ranging slotto be used by the MS 16. Also at step 1432, the BS 14 determines anAccess ID for the MS 16. The Access ID is as yet unknown to the MS 16.The Access ID can be used by the BS 14 as an address, encryption key orscrambling code for content destined for the MS 16 during the rangingoperation.

The BS 14 then proceeds to formulate a ranging response message 1434,which is sent to the MS 16. Ranging response message 1434 specifies thatranging is to continue, and provides any necessary adjustments to thetiming/frequency/power characteristics of the uplink signal. Inaddition, ranging response message 1434 specifies the ranging codeand/or ranging slot that were used by the MS 16 to transmit rangingmessage 1424. This allows the MS 16 to recognize that ranging responsemessage 1434 is actually destined for it. In addition, ranging responsemessage 1434 identifies the assigned ranging code and/or assignedranging slot to be used by the MS 16 next time. In addition, rangingresponse message 1434 includes the Access ID mentioned above.

Ranging response message 1434 is then received at the MS 16. The MS 16executes step 1426 and determines that ranging response message 1434 isindeed a ranging response message destined for the MS. In particular,this can be determined based on fact that the ranging code and/orranging slot that the MS 16 previously used are present in rangingresponse message 1434. Therefore, the MS 16 takes the “Y” branch out ofstep 1426. Also, the MS 16 stores the received Access ID in a memory forfuture use. Also, the MS 16 makes the requisite adjustments to thepower/time/frequency characteristics it uses in the uplink direction.The MS 16 then proceeds to formulate another ranging message 1436characterized by a set of ranging resources (and also the adjustedtime/frequency/power) characteristics. This time, the MS 16 uses theassigned ranging code and the assigned ranging slot received from the BS14 in ranging response message 1434.

The BS 14 receives ranging message 1436 and determines whether theranging operation is successful (step 1438). The outcome of step 1438may be that the BS 14 has determined that the ranging operation was asuccess, in which case the BS 14 proceeds to issue a ranging responsemessage 1448 indicative of this determination. However, it is possibleat this stage that the previous power/time/frequency adjustments werenot sufficient. The outcome of step 1438 may therefore be that the BS 14has determined that the ranging operation was not a success. In thiscase, the BS 14 proceeds to step 1440 where a further parameteradjustment is calculated. This may again affect one or more of thefrequency, timing and power that characterize the signaling used by theMS 16. Various algorithms can be used to determine an adjustment of thepower, timing and/or frequency characteristics of the uplink signal.Also at step 1440, the BS 14 may, but need not, calculate a new rangingcode and/or a new ranging slot to be used by the MS 16.

The BS 14 then proceeds to formulate a ranging response message 1442,which is sent to the MS 16. Ranging response message 1442 specifies thatranging is to continue, as well as provides any necessary furtheradjustments to the timing/frequency/power characteristics of the uplinksignal. In addition, ranging response message 1442 specifies the AccessID that had previously been sent to the MS 16 in ranging responsemessage 1434. The Access ID allows the MS 16 to recognize that rangingresponse message 1442 is destined for it. It is therefore not necessaryto transmit in ranging response message 1442 the ranging code and/orranging slot that were used by the MS 16 to transmit ranging message1436. In addition, ranging response message 1442 identifies the assignedranging code and/or assigned ranging slot, if computed at step 1440, tobe used by the MS 16 in the future.

At step 1444, the MS 16 makes the requisite adjustments to thepower/time/frequency characteristics it uses in the uplink direction.The MS 16 then proceeds to formulate another ranging message 1446characterized by a set of ranging resources (and also the adjustedtime/frequency/power) characteristics. The MS 16 uses either the rangingcode and the ranging slot it had used in the past or it uses theassigned ranging code and/or the assigned ranging slot specified by theMS 16 in ranging response message 1442. The BS 14 receives rangingmessage 1446 from the MS 16 and determines whether the ranging operationis successful (step 1438). If the outcome of step 1438 is that the BS 14has determined that the ranging operation was not a success, then the BS14 returns to step 1440. However, at some point, the ranging operationwill be considered to have been successful, and the BS 14 proceeds toissue a ranging response message 1448 indicative of this determination.Ranging response message 1448 also includes the Access ID identifyingthe MS 16. However, a lengthy MAC address is not required.

The BS 14 then issues a granting message 1452, which schedules the nextuplink transmission from the MS 16. In this case, the next uplinktransmission from the MS 16 is a ranging request message 1454 containingthe global address (e.g., the 48-bit MAC address) of the MS 16. Forexample, the ranging request message 1454 could take a form similar toan RNG-REQ message as defined in IEEE 802.16 or 802.16m. Receipt of theglobal address by the BS 14 allows the BS 14 to determine the trueidentity of the MS 16 with which the ranging operation has completedsuccessfully. Thus, at step 1456, the BS 14 determines the MS ID basedon the global address.

This can be done by looking up the MS ID in a table in a memory, basedon the global address. Alternatively, the MS ID can be assigned from apool of addresses or identifiers, and stored in association with theglobal address.

The BS 14 then sends a ranging response message 1458 to the MS 16,containing the MS ID, as well as the Access ID identifying the MS. TheMS 16 receives the ranging response message 1458, and determines that itis the recipient of this message (based on the Access ID). The MS 16proceeds to extract the MS ID and store it in a memory. With the rangingoperation now complete, the MS 16 enters the Connected state. The MS 16uses the MS ID in future communication with the network during theConnected state. Future communication can include transmission and/orreception of data in association with management connections and trafficconnections.

It should be appreciated that because the Access ID is designed for usespecifically during the ranging operation, and because only a limitednumber of mobile stations will perform ranging at any given time, theAccess ID can be limited to a small number of bits and, in particular,fewer than 16 bits. As an example, the 8-10 bit range may be suitable asa length of the Access ID. Also, the fact that the same Access ID couldconceivably be recycled by different mobile stations performing rangingat different non-overlapping times, the Access ID does not have aone-to-one mapping to a given MS's global address. This preservesanonymity and enhances security.

Also, because during the Connected state the MS 16 can be identified bythe MS ID rather than its global address, and because the MS ID is localto the domain of the serving BS, a similarly small number of bits can beused and, in particular, fewer than 16 bits. Again, the 8-10 bit rangemay be suitable, by way of example. However, this does not imply thatthe Access ID and the MS ID need to be of the same length.

It will also be appreciated that the comparatively short length of theAccess ID and MS ID cause shortening of the granting message (e.g.,UL-MAP), the ranging response message (e.g., RNG-RSP) and the rangingrequest message (e.g., RNG-REQ). The DL-MAP, DCD and UCD messages wouldsimilarly benefit from a reduced length.

A first alternative embodiment is now described with reference to theflow diagram in FIG. 16. Specifically, consider that the outcome of step1438 is that the BS 14 has determined that the ranging operation was nota success. In this case, the BS 14 proceeds to step 1640 where a furtherparameter adjustment is calculated. This may again affect one or more ofthe frequency, timing and power that characterize the signaling used bythe MS 16. Various algorithms can be used to determine an adjustment ofthe power, timing and/or frequency characteristics of the uplink signal.Also at step 1640, the BS 14 calculates a new ranging code and a newranging slot to be used by the MS 16. As ranging continues, the rangingresources assigned correspond to ranging channels with progressivelysmaller timing offsets. For example, initial ranging attempts may besent in a ranging region that spans 6 symbols which is intended toaccommodate larger ranging timing offsets. As ranging progresses, the BS14 can assign ranging resources to the MS 16 that span progressivelyshorter durations, such as 3 and then 2 symbols. The final rangingresource assigned may only accommodate synchronization to within an OFDMcyclic prefix length. (The final ranging resource assigned may also beretained by the MS 16 for periodic ranging.)

The BS 14 then proceeds to formulate a ranging response message 1642,which is sent to the MS 16. Ranging response message 1642 specifies thatranging is to continue, as well as provides any necessary furtheradjustments to the timing/frequency/power characteristics of the uplinksignal. In addition, ranging response message 1642 identifies theassigned ranging code and the assigned ranging slot to be used by the MS16 in the future. Indeed, at step 1444, the MS 16 makes the requisiteadjustments to the power/time/frequency characteristics it uses in theuplink direction. The MS 16 then proceeds to formulate another rangingmessage 1646 characterized by a set of ranging resources (and also theadjusted time/frequency/power) characteristics. The MS 16 uses theassigned ranging code and the assigned ranging slot specified by the MS16 in ranging response message 1642.

A second alternative embodiment is now described with reference to theflow diagram in FIG. 17. Specifically, in this alternative embodiment,once the ranging code and ranging slot used in a ranging message arereceived (“heard”) b the BS 14, the MS 16 continues to use the sameranging code and ranging slot until the BS 14 generates a rangingresponse message indicative of successful ranging.

Alternatively or in addition, the MS 16 and BS 14 use sequences (or“scrambling codes”) for scrambling communications between the twoentities. A first such sequence is an “initial ranging sequence” and asecond such sequence is a “continued ranging sequence”. As shown in FIG.17, the initial ranging sequence is used by the MS 16 to scramble theranging messages it sends before it receives the first ranging responsemessage from the BS 14. Also as shown in FIG. 17, the initial rangingsequence is also used by the BS 14 to scramble messages sent to the MS16 before the MS 16 has received the Access ID. Also as shown in FIG.17, the continued ranging sequence (or, optionally, the initial rangingsequence) can be used by the MS 16 to scramble the ranging messages itsends between receiving the first ranging response message from the BS14 and receipt of the MS ID. Thus, it is assumed that the initialranging sequence (and, if used, the continued ranging sequence) areknown to the BS 14 and the MS 16. Also as shown in FIG. 17, after the MS16 has received the Access ID, the BS 14 scrambles messages destined forthe MS 16 using the Access ID. Clearly, the appropriate descramblingneeds to be performed by the recipient and therefore prior knowledge ofthe appropriate scrambling code is needed. For this reason, it is onlyafter the MS 16 has been informed of the Access ID that messagesdestined for the MS 16 can be scrambled using the Access ID.

Scenario B

In Scenario B, the MS 16 becomes involved in a ranging operation uponre-entering the network (e.g., after having been in the Idle state,after having left the network to use a different one, then returned(i.e., roaming), etc.). Thus, in this scenario, synchronization isassumed to have been maintained. Reference is now made to the flowdiagram in FIG. 18, which shows the actions of the BS 14 and MS 16 whilethe MS 16 is in the Access state. It should be appreciated that rangingcan occur autonomously (i.e., MS-initiated) or in response to a pagingmessage 1809 from the BS 14 while the MS 16 is in the Paging Availablemode of the Idle state. In the case of a received paging message 1809,the paging message 1809 can specify the set of dedicated rangingresources to be used by the MS 16, such as a dedicated ranging code anda dedicated ranging slot.

The BS 14 issues an uplink granting message 1810 (e.g., a UL-MAPmessage) which defines an initial ranging interval to be used by the MS16 in the uplink frame. The contents of the uplink granting messagecould be formulated by an uplink scheduler in the BS 14. The uplinkscheduler manages uplink bandwidth, and schedules MSs that will beallocated uplink grants based on the QoS requirements of their serviceflow(s) and bandwidth requests. An uplink grant allocated by the uplinkscheduler is directed towards a reserved FID (e.g., broadcast) and canuse a predefined robust profile with BPSK ½ modulation/FEC, for example.After transmission of granting message 1810, the BS 14 continues tooperate normally (1812). This includes the periodic issuance of othergranting messages, such as granting message 1822.

Meanwhile, as shown at 1812, the MS 16 has been waiting for receipt of agranting message and is assumed to ultimately receive granting message1810. Upon receipt of the granting message 1810, the MS 16 formulates aranging message 1816 characterized by the set of dedicated rangingresources specified in the paging message 1809. This includes adedicated ranging code and/or a dedicated ranging slot.

If the BS 14 properly detects the presence of the dedicated ranging codein the dedicated ranging slot of ranging message 1816, then the BS 14issues a ranging response message to the MS 16. For example, the rangingresponse message could take a form similar to an RNG-RSP message asdefined in IEEE 802.16 or 802.16m. In anticipation of this event, atstep 1826, the MS 16 determines whether an RNG-RSP message has beenreceived from the BS 14. If a certain amount of time has elapsed, and aRNG-RSP message has not been received, then this means that the BS 14has not properly detected the presence of the dedicated ranging code inthe dedicated ranging slot of ranging message 1816. This could be for avariety of reasons, including power issues, interference, etc.Meanwhile, the MS 16 is also attentive to receipt of further grantingmessages (step 1820). If indeed the aforementioned granting message 1822is received without having receiving an intervening RNG-RSP message fromthe BS 14, then the MS 16 will be granted a new ranging interval in anuplink frame.

In response, and similar to what was described earlier, the MS 16formulates a ranging message 1824 that is characterized by the same setof dedicated ranging resources. If the BS 14 properly detects thepresence of the dedicated ranging code in the dedicated ranging slot ofranging message 1824, then the BS 14 will issue a ranging responsemessage to the MS 16. In anticipation of this event, at step 1826, theMS 16 determines whether a ranging response message has been receivedfrom the BS 14. If a certain amount of time has elapsed, and a rangingresponse message still has not been received, then the MS 16 willreceive yet another granting message at step 1820 and so on. However, ifthe BS 14 does properly detect the presence of the dedicated rangingcode in the dedicated ranging slot of ranging message 1824 (step 1828),then the BS 14 will determine whether the ranging operation issuccessful (step 1830). In other words, just because the BS 14 can hearthe MS 16 does not mean that the MS 16 is using adequate power, timingand frequency parameters.

Thus, the outcome of step 1830 may be that the BS 14 has determined thatthe ranging operation was a success, in which case the BS 14 proceeds toissue a ranging response message 1850 indicative of this determination.On the other hand, the outcome of step 1830 may be that the BS 14 hasdetermined that the ranging operation was not a success. In this case,the BS 14 proceeds to step 1832 where a parameter adjustment iscalculated. This may affect one or more of the frequency, timing andpower that characterize the signaling used by the MS 16. Variousalgorithms can be used to determine an adjustment of the power, timingand/or frequency characteristics of the uplink signal. Also at step1832, the BS 14 optionally calculates a new ranging code and/or a newranging slot to be used by the MS 16. Also at step 1832, the MS 16determines an Access ID for the MS 16. The Access ID is as yet unknownto the MS 16.

The Access ID can be used by the BS 14 as an address, encryption key orscrambling code for content destined for the MS 16 during the rangingoperation. The BS 14 then proceeds to formulate a ranging responsemessage 1834, which is sent to the MS 16. Ranging response message 1434specifies that ranging is to continue, and provides any necessaryadjustments to the timing/frequency/power characteristics of the uplinksignal. In addition, ranging response message 1834 specifies the rangingcode and/or ranging slot that were used by the MS 16 to transmit rangingmessage 1824. This allows the MS 16 to recognize that ranging responsemessage 1834 is actually destined for it. In addition, ranging responsemessage 1834 optionally identifies the new ranging code and/or newranging slot determined at step 1832. In addition, ranging responsemessage 1834 includes the Access ID mentioned above.

The BS 14 then proceeds to formulate a ranging response message 1834,which is sent to the MS 16. Ranging response message 1434 specifies thatranging is to continue, and provides any necessary adjustments to thetiming/frequency/power characteristics of the uplink signal. Inaddition, ranging response message 1834 specifies the ranging codeand/or ranging slot that were used by the MS 16 to transmit rangingmessage 1824. This allows the MS 16 to recognize that ranging responsemessage 1834 is actually destined for it. In addition, ranging responsemessage 1834 optionally identifies the new ranging code and/or newranging slot determined at step 1832. In addition, ranging responsemessage 1834 includes the Access ID mentioned above.

Ranging response message 1834 is then received at the MS 16. The MS 16executes step 1826 and determines that ranging response message 1834 isindeed a ranging response message destined for the MS. In particular,this can be determined based on fact that the ranging code and/orranging slot that the MS 16 previously used are present in rangingresponse message 1834. Therefore, the MS 16 takes the “Y” branch out ofstep 1826. Also, the MS 16 stores the received Access ID in a memory forfuture use. Also, the MS 16 makes the requisite adjustments to thepower/time/frequency characteristics it uses in the uplink direction.The MS 16 then proceeds to formulate another ranging message 1836characterized by a set of ranging resources (and also the adjustedtime/frequency/power) characteristics. The MS 16 uses the either thededicated ranging code and the dedicated ranging slot, or the newranging code and the new ranging slot received from the BS 14 in rangingresponse message 1834.

The BS 14 receives ranging message 1836 and determines whether theranging operation is successful (step 1838). The outcome of step 1838may be that the BS 14 has determined that the ranging operation was asuccess, in which case the BS 14 proceeds to issue a ranging responsemessage 1848 indicative of this determination. However, it is possibleat this stage that the previous power/time/frequency adjustments werenot sufficient. The outcome of step 1838 may therefore be that the BS 14has determined that the ranging operation was not a success. In thiscase, the BS 14 proceeds to step 1840 where a further parameteradjustment is calculated. This may again affect one or more of thefrequency, timing and power that characterize the signaling used by theMS 16. Various algorithms can be used to determine an adjustment of thepower, timing and/or frequency characteristics of the uplink signal.Also at step 1840, the BS 14 may, but need not, calculate another new(“newer”) ranging code and/or another new (“newer”) ranging slot to beused by the MS 16.

The BS 14 then proceeds to formulate a ranging response message 1842,which is sent to the MS 16. Ranging response message 1842 specifies thatranging is to continue, as well as provides any necessary furtheradjustments to the timing/frequency/power characteristics of the uplinksignal. In addition, ranging response message 1842 specifies the AccessID that had previously been sent to the MS 16 in ranging responsemessage 1834. The Access ID allows the MS 16 to recognize that rangingresponse message 1842 is destined for it. It is therefore not necessaryto transmit in ranging response message 1842 the ranging code and/orranging slot that were used by the MS 16 to transmit ranging message1836. In addition, ranging response message 1842 identifies the newerranging code and/or the newer ranging slot, if computed at step 1840, tobe used by the MS 16 in the future.

At step 1844, the MS 16 makes the requisite adjustments to thepower/time/frequency characteristics it uses in the uplink direction.The MS 16 then proceeds to formulate another ranging message 1846characterized by a set of ranging resources (and also the adjustedtime/frequency/power) characteristics. The MS 16 uses either thededicated ranging code and the dedicated ranging slot, or the newranging code and the new ranging code it (may have) used last time, orthe newer ranging code and the newer ranging slot specified by the MS 16in ranging response message 1842. The BS 14 receives ranging message1846 from the MS 16 and determines whether the ranging operation issuccessful (step 1838). If the outcome of step 1838 is that the BS 14has determined that the ranging operation was not a success, then the BS14 returns to step 1840. However, at some point, the ranging operationwill be considered to have been successful, and the BS 14 proceeds toissue a ranging response message 1848 indicative of this determination.Ranging response message 1848 also includes the Access ID identifyingthe MS 16. However, a lengthy MAC address is not required.

The BS 14 then issues a granting message 1852, which schedules the nextuplink transmission from the MS 16. In this case, the next uplinktransmission from the MS 16 is a ranging request message 1854 containingthe Idle ID of the MS 16. For example, the ranging request message 1854could take a form similar to an RNG-REQ message as defined in IEEE802.16 or 802.16m. Receipt of the Idle ID by the BS 14 allows the BS 14to determine the true identity of the MS 16 with which the rangingoperation has completed successfully. This is because the Idle ID isuniquely mapped to the MS 16. At step 1856, the BS 14 determines theAccess ID based on the Idle ID. This can be done by looking up the MS IDin a table in a memory, based on the Idle ID, which may or may notinvolve an intermediate step of determining the global address.Alternatively, the MS ID can be assigned from a pool of addresses oridentifiers, and stored in association with the Idle ID.

The BS 14 then sends a ranging response message 1858 to the MS 16,containing the MS ID, as well as the Access ID identifying the MS. TheMS 16 receives the ranging response message 1858, and determines that itis the recipient of this message (based on the Access ID). The MS 16proceeds to extract the MS ID and store it in a memory. With the rangingoperation now complete, the MS 16 enters the Connected state. The MS 16uses the MS ID in future communication with the network during theConnected state. Future communication can include transmission and/orreception of data in association with management connections and trafficconnections.

A first alternative embodiment can incorporate changes to FIG. 18similar to those that modified the flow diagram in FIG. 16.

A second alternative embodiment can incorporate changes to FIG. 18similar to those that modified the flow diagram in FIG. 17.

Scenario C

In Scenario C, the MS 16 becomes involved in a ranging operation inorder to carry out a location update while in the Idle state. Thelocation update can occur autonomously (i.e., MS-initiated) or inresponse to a paging message from the BS 14 while the MS 16 is in thePaging Available mode of the Idle state. Specifically, the MS in Idlemode can perform a location update process operation if one of followinglocation update trigger conditions is met:

-   -   Paging group location update: The MS 16 performs the Location        Update process when the MS 16 detects a change in paging group.        The MS 16 detects the change of paging group by monitoring the        Paging Group IDs, which are transmitted by the BS 14;    -   Timer based location update: The MS 16 periodically performs        location update process prior to the expiration of idle mode        timer;    -   Power down location update: The MS 16 attempts to complete a        location update once as part of its orderly power down        procedure;    -   Multicast/broadcast (MBS) location update: When receiving MBS        data in the Idle state, during MBS zone transition, the MS 16        may perform a MBS location update process to acquire the MBS        zone information for continuous reception of MBS data.

Reference is now made to the flow diagram in FIG. 19, which shows theactions of the BS 14 and MS 16 while the MS 16 performs a locationupdate while in the Idle state. Specifically, the description fromreference numeral 1809 up until the point where the MS 16 issues rangingrequest message 1854 containing the Idle ID of the MS 16 is identical tothat given above with reference to FIG. 18. The ranging request message1854 may be also formulated to indicate that it is a location update andnot occurring in the context of network entry. At step 1956, the BS 14,which is in receipt of ranging request message 1854, acknowledges thelocation update. This can be done by issuing a ranging response message1958 to the MS 16, containing a location update acknowledgement, as wellas the Access ID identifying the MS. The MS 16 receives the rangingresponse message 1958, and determines that it is the recipient of thismessage (based on the Access ID). With the ranging operation nowcomplete, the MS 16 goes back into the Idle state until a furtherlocation update is required or until it is commanded to enter into theConnected state. The MS 16 uses the Idle ID in future communication withthe network during the Idle state.

A first alternative embodiment can incorporate changes to FIG. 19similar to those that modified the flow diagram in FIG. 16.

A second alternative embodiment can incorporate changes to FIG. 19similar to those that modified the flow diagram in FIG. 17.

It should be appreciated that many variants of the above embodiments arepossible. Specifically, messages may be scrambled, encoded or encryptedin any desired fashion. In particular, the scrambling techniquesdescribed with reference to FIG. 17 could be applied to any of the othermessage flow diagrams, in order to enhance security, reduce peak poweror for other reasons.

In addition, although the above messages have been described in thecontext of the IEEE 802.16 and IEEE 820.16m mobile communicationstandards, it should be appreciated that the present invention can bemore broadly applied to other communication systems, including thosebeing implemented or designed in accordance with other mobilecommunication standards, such as the Long Term Evolution (LTE) standardbeing promulgated by the Third Generation Partnership Project (3GPP).

In addition, although the above description has focused on initialranging using an Access ID and an MS ID, it should be appreciated thatthe MS 16 may effect periodic ranging using one or both of theseidentifiers.

In addition, although the above description has focused on apoint-to-multipoint (PMP) implementation using an orthogonal frequencydivision multiple access (OFDMA) PHY layer, it should be appreciatedthat embodiments of the present invention may apply to otherimplementations and PHY layers, including a mesh implementation, as wellas a single carrier (SC) PHY, a single-carrier access (SCa) PHY andorthogonal frequency division multiplexing (OFDM) PHY. For example, inthe SC, SCa and OFDM PHY layers, rather than sending a ranging code, theMS may send a RNG-REQ message in an initial ranging interval. Also, theMAC protocol used may support Time Division Duplexing (TDD) and/orfrequency division duplexing (FDD).

In addition, it should be appreciated that embodiments of the presentinvention can be applied to relay stations (RSs). More specifically, aRS can behave such as to allow the MS to interact as if it wereinteracting with a BS, while behaving such as to allow the BS tointeract as if it were interacting with a MS. Meanwhile, the RS mayimplement one or more of the above described features with respect toinitial ranging.

The foregoing figures and description provide one specific example of acommunication system that could be used to implement embodiments of theapplication. It is to be understood that embodiments of the applicationcan be implemented with communications systems having architectures thatare different than the specific example, but that operate in a mannerconsistent with the implementation of the embodiments as describedherein.

Those skilled in the art will appreciate that in some embodiments, theMS 16 and/or the BS 14 may comprise one or more computing apparatusesthat have access to a code memory (not shown) which storescomputer-readable program code (instructions) for operation of the oneor more computing apparatuses, thereby allowing one or more of the abovedescribed functions to be carried out. The computer-readable programcode could be stored on a medium which is fixed, tangible and readabledirectly by the one or more computing apparatuses, (e.g., removablediskette, CD-ROM, ROM, fixed disk, USB drive), or the computer-readableprogram code could be stored remotely but transmittable to the one ormore computing apparatuses via a modem or other interface device (e.g.,a communications adapter) connected to a network (including, withoutlimitation, the Internet) over a transmission medium, which may beeither a non-wireless medium (e.g., optical or analog communicationslines) or a wireless medium (e.g., microwave, infrared or othertransmission schemes) or a combination thereof. In other embodiments,the MS 16 and/or the BS 14 may comprise pre-programmed hardware orfirmware elements (e.g., application specific integrated circuits(ASICs), electrically erasable programmable read-only memories(EEPROMs), flash memory, etc.), or other related components that allowone or more of the above described functions to be carried out.

Additional modifications and variants are possible, and the scope of thepresent invention is only to be limited by the claims appended hereto.

What is claimed is:
 1. A method, comprising: at a base station:generating a temporary mobile station identifier for a mobile station;transmitting, to the mobile station, the temporary mobile stationidentifier during an access procedure involving the mobile station,wherein the mobile station uses the temporary mobile station identifierto extract the contents of a first message received from the basestation during the access procedure; and transmitting, to the mobilestation, a further mobile station identifier based on a global addressof the mobile station, wherein the mobile station uses the furthermobile station identifier to extract the contents of a second messagereceived from the base station.
 2. The method of claim 1, furthercomprising: receiving, from the mobile station, a request to perform theaccess procedure, the request including a random access code.
 3. Themethod of claim 2, wherein the generating the temporary mobile stationidentifier is based on the random access code.
 4. The method of claim 1,wherein the contents of the second message include an uplink grant forthe mobile station.
 5. The method of claim 1, wherein the further mobilestation identifier is generated by the Medium Access Control (MAC) layerof the base station.
 6. The method of claim 1, wherein the first messagefurther comprises at least one of a ranging code or a ranging slotpreviously used by the mobile station, wherein the ranging code or theranging slot allows the mobile station to determine that the message isdestined for the mobile station.
 7. The method of claim 1, wherein thesecond message is received from the base station after the accessprocedure is complete.
 8. The method of claim 1, wherein the secondmessage is received from the base station during the access procedure.9. A base station, comprising: a processor generating a temporary mobilestation identifier during an access procedure involving a mobilestation, wherein the mobile station uses the temporary mobile stationidentifier to extract the contents of a first message received from thebase station during the access procedure and generating a further mobilestation identifier based on a global address of the mobile station,wherein the mobile station uses the further mobile station identifier toextract the contents of a second message received from the base station;and transmit circuitry configured to output the first and secondmessages to the mobile station.
 10. The base station of claim 9, furthercomprising: receive circuitry configured to receive a request from themobile station to perform the access procedure, the request including arandom access code.
 11. The base station of claim 10, wherein the randomaccess code is communicated to the processor which generates thetemporary mobile station identifier based on the random access code. 12.The base station of claim 9, wherein the contents of the second messageinclude an uplink grant for the mobile station.
 13. The base station ofclaim 9, wherein the further mobile station identifier is generated bythe Medium Access Control (MAC) layer being executed by the processor ofthe base station.
 14. The base station of claim 9, wherein the secondmessage is received from the base station after the access procedure iscomplete.
 15. The base station of claim 9, wherein the second message isreceived from the base station during the access procedure.
 16. A basestation, comprising: a processor; and a non-transitory computer readablestorage medium comprising a set of instructions, that when executed,cause the processor to perform operations comprising: generating atemporary mobile station identifier for a mobile station; transmitting,to the mobile station, the temporary mobile station identifier during anaccess procedure involving the mobile station, wherein the mobilestation uses the temporary mobile station identifier to extract thecontents of a first message received from the base station during theaccess procedure; and transmitting, to the mobile station, a furthermobile station identifier based on a global address of the mobilestation, wherein the mobile station uses the further mobile stationidentifier to extract the contents of a second message received from thebase station.
 17. The base station of claim 16, wherein the operationsfurther comprise: receiving, from the mobile station, a request toperform the access procedure, the request including a random accesscode.
 18. The base station of claim 17, wherein the generating thetemporary mobile station identifier is based on the random access code.19. The method of claim 16, wherein the contents of the second messageinclude an uplink grant for the mobile station.
 20. The base station ofclaim 16, wherein the second message is received from the base stationafter the access procedure is complete.
 21. The base station of claim16, wherein the second message is received from the base station duringthe access procedure.